Magnetic spectrometer for measuring gamma ray energy-time combined spectrum and implementation method

Abstract

The invention discloses a magnetic spectrometer for measuring a gamma ray energy-time combined spectrum and an implementation method, and relates to the field of gamma ray energy spectrum measurement. The system comprises a gamma-e conversion target and an electron beam limiting device which are arranged in a first vacuum chamber, a magnetic analyzer system arranged in a second vacuum chamber, and a scintillation optical fiber detector system, the magnetic analyzer system comprises a heterogeneous deflection magnet and a special-shaped vacuum box arranged in a magnetic gap of the heterogeneous deflection magnet; the longitudinal section of an exit port of the heterogeneous deflection magnet is arranged to be parabola-shaped; the scintillation optical fiber detector system comprises a scintillation optical fiber array used for receiving charged particle beams emitted from the heterogeneous deflection magnets, a photoelectric receiving unit used for receiving photons emitted by the scintillation optical fiber array, and a high-speed data acquisition device used for recording output waveforms. Gamma-ray energy spectrum information and time spectrum information which are wide in energy range and high in resolution can be obtained while the equipment is light in weight.

Description

Technical Field

[0001] The present invention relates to the field of gamma-ray energy spectrum measurement, and in particular to a magnetic spectrometer for measuring a gamma-ray energy-time joint spectrum and an implementation method thereof. Background Art

[0002] New pulse radiation sources represented by laser inverse Compton scattering sources, free electron lasers, advanced synchrotron radiation and laser plasma acceleration are important tools for cutting-edge research in the world. Their related design and performance research is also one of the most active research fields in the world. In recent years, with the development of laser technology, laser inverse Compton scattering technology based on the inverse Compton scattering principle, which uses the collision of high-energy electron beams and high-power laser scattering to produce ultrafast, quasi-monoenergetic gamma-ray beams, has developed rapidly. Gamma energy spectrum, as an important parameter of pulse radiation field, can directly reflect the state of radiation source and is related to the calculation of related parameters such as radiation dose and equivalent sensitivity of detector. Therefore, gamma energy spectrum measurement is an important part of pulse radiation field diagnosis, which is of great significance to the development, performance test diagnosis and application of pulsed X / γ-ray sources and the research of pulsed ray physics.

[0003] In the prior art, commonly used gamma spectrum measurement methods include attenuation method, Bragg crystal diffraction method, single photon measurement method and magnetic spectrometer method. Among them, the magnetic spectrometer method is often used for spectrum measurement of high-intensity pulsed gamma-ray sources. Since the 1980s, Los Alamos National Laboratory (LANL), Lawrence Livermore National Laboratory (LLNL), Northwest Institute of Nuclear Technology and China Academy of Engineering Physics have successively developed gamma spectrum magnetic analysis technology. In 2012, LANL proposed a gamma electron magnetic spectrometer (GEMS) based on the needs of the National Ignition Facility (NIF) for the measurement of prompt gamma spectrum in high-yield DT implosion experiments, but this device is bulky and weighs 1887kg. In 2014, the University of Belfast in the UK and Rice University in the United States successively reported spectrometers for all-optical inverse Compton gamma light sources, but the energy resolution was relatively low, reaching only a resolution level of 10%-15%. In 2018, the Australian Science and Research Council's (ASCR) also reported a single high-energy gamma spectrometer for inverse Compton scattering experiments, and conducted multiple sets of bremsstrahlung energy spectrum measurement experiments, but it also had the problem of low energy resolution. In 2020, the University of Science and Technology of China reported a small high-bandwidth Compton magnetic spectrometer that combines the inhomogeneous magnetic field generated by a stepped permanent magnet and a curved detector, which broadens the measurement bandwidth while reducing the size and weight of the magnetic spectrometer. However, the resolution levels of this device in different energy bands vary greatly, and the time spectrum information cannot be detected due to the use of (Imaging Plate, IP) plate imaging.

[0004] In summary, the existing technology cannot achieve lightweight equipment and at the same time perform time-intensity waveform measurement of gamma rays in a wide energy range under high energy resolution conditions. Summary of the invention

[0005] Based on this, it is necessary to provide a magnetic spectrometer and implementation method for measuring the gamma-ray energy-time joint spectrum in order to address the technical problem that the existing technology cannot achieve lightweight equipment while measuring the time-intensity waveform of gamma rays in a wide energy range under high energy resolution conditions.

[0006] The present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a magnetic spectrometer for measuring a gamma-ray energy-time joint spectrum, comprising a γ-e conversion target 2 and an electron beam limiter 4 arranged in a first vacuum chamber 3, a magnetic analyzer system arranged in a second vacuum chamber 5, and a scintillation fiber detector system 8;

[0008] The magnetic analyzer system comprises a heterogeneous deflection magnet 6 and a heterogeneous vacuum box 7 arranged in the magnetic gap of the heterogeneous deflection magnet; the longitudinal section of the exit port of the heterogeneous deflection magnet is arranged to be parabolic;

[0009] The γ-e conversion target is used to convert the received gamma rays into a charged particle beam, the electronic beam limiter is used to focus the charged particle beam, and the special-shaped vacuum box is used to provide a vacuum environment for the charged particle beam in the special-shaped deflection magnet;

[0010] The scintillation fiber detector system comprises: a scintillation fiber array 9 for receiving the charged particle beam emitted from the heterogeneous deflection magnet and a photoelectric receiving unit for receiving photons emitted by the scintillation fiber array;

[0011] The gamma-e conversion target, the electron beam limiter, the heterogeneous deflection magnet and the scintillating optical fiber array are sequentially arranged in the propagation path of the charged particle beam.

[0012] Furthermore, the expression of the parabola is:

[0013] z=-1.38x 2 ;

[0014] Wherein, z represents the distance between the bottom of the parabola and the straight line connecting the two endpoints of the parabola, and x represents the distance between the two endpoints of the parabola.

[0015] Furthermore, the deflection radius of the heterogeneous deflection magnet is 200 mm, the deflection angle is 90 degrees, and the incident edge angle and the exit edge angle are 61 degrees and 0 degrees respectively.

[0016] Further, the electron beam limiter comprises an inner layer structure and an outer layer structure;

[0017] Wherein, the materials of the inner layer structure include: graphite and polyethylene;

[0018] The materials of the outer layer structure include: tungsten, lead, copper, iron and stainless steel.

[0019] Furthermore, the material of the γ-e conversion target is any one of lithium, beryllium, boron and carbon.

[0020] Further, the type of the heterogeneous deflection magnet is an electromagnet or a permanent magnet. In the case where the type of the heterogeneous deflection magnet is an electromagnet, the heterogeneous deflection magnet is connected to a power supply control system;

[0021] The power control system is used to adjust the current in the coil of the heterogeneous deflection magnet to control the magnetic field strength of the heterogeneous deflection magnet.

[0022] In a second aspect, the present invention provides a method for measuring a gamma-ray energy-time joint spectrum using a magnetic spectrometer based on the gamma-ray energy-time joint spectrum, characterized in that it comprises:

[0023] converting the gamma rays into charged particle beams using the γ-e conversion target;

[0024] The charged particle beam is screened by the electronic beam limiter, and the screened charged particle beam is double-focused and angular dispersion is eliminated by the heterogeneous deflection magnet, so that charged particles with different energies in the charged particle beam are separated to different horizontal positions;

[0025] The scintillating fiber array is used to receive the charged particles separated to different horizontal positions emitted by the heterogeneous deflection magnet, and a corresponding number of photons are emitted based on the energy deposited by the charged particles at different horizontal positions on the scintillating fiber array;

[0026] The photons corresponding to different energies are transmitted to the photoelectric receiving unit by using a transmission optical fiber, and are detected by a pulse current method. An oscilloscope and a high-speed data acquisition device are used to record the output waveform to obtain horizontal position distribution information of the charged particles with different energies and time and intensity waveform information of the charged particle beam. A gamma-ray energy-time joint spectrum is constructed based on the time and intensity waveform information.

[0027] Furthermore, the type of the heterogeneous deflection magnet is an electromagnet or a permanent magnet. In the case where the type of the heterogeneous deflection magnet is an electromagnet, the method further includes:

[0028] Adjusting the current value in the coil of the heterogeneous deflection magnet to control the heterogeneous deflection magnet to generate magnetic fields of different strengths;

[0029] According to the magnetic fields of different strengths, different energy ranges for performing double focusing on the charged particle beam and eliminating angular dispersion are obtained.

[0030] The at least one technical solution adopted by the present invention can achieve the following beneficial effects:

[0031] The present invention designs the shape of the exit port of the heterogeneous deflection magnet to be a parabola, and can focus the charged particle beam in a direction perpendicular to the plane where the heterogeneous deflection magnet is located through the edge magnetic field focusing effect of the exit port of the heterogeneous deflection magnet, and corrects the different exit angles caused by the charged particles being deflected in the deflection magnetic field due to different incident angles through the curvature of each point of the parabola, so that the exit position in the horizontal direction of the exit port of the heterogeneous deflection magnet is independent of the incident angle, thereby realizing double focusing of the charged particle beam. In addition, the design of the parabolic exit port can increase the path length of particles that deviate from the axis of the charged particle beam in the deflection magnetic field, so that particles on both sides of the axis of the charged particle beam are affected by the focusing effect and the defocusing effect at the same time. It can replace the traditional six-pole magnet to eliminate the angular dispersion generated by the charged particle beam during the deflection process, so that the focal plane (the plane formed by connecting the focusing points of the charged particles) is perpendicular to the exit direction, so that there is no need to add an additional six-pole magnet, and the dual focusing and angular dispersion elimination capabilities of the charged particles in the deflection magnetic field process are concentrated on one magnet, thereby achieving lightweight equipment and high energy resolution conditions for time-intensity waveform measurement of gamma rays in a wide energy range (several hundred keV to more than ten MeV). BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0033] Figure 1 A schematic diagram of the overall structure of a magnetic spectrometer for measuring a gamma-ray energy-time joint spectrum provided by the present invention;

[0034] Figure 2 A schematic top view of a heterogeneous deflection magnet of a magnetic spectrometer for measuring a gamma-ray energy-time joint spectrum provided by the present invention;

[0035] Figure 3 A schematic diagram of the motion path of a charged particle beam deflected in a heterogeneous deflection magnet provided by the present invention;

[0036] Figure 4 A schematic flow chart of a method for measuring a gamma-ray energy-time joint spectrum provided by the present invention;

[0037] Reference numerals:

[0038] 1. Gamma particle beam source, 2. γ-e conversion target, 3. Vacuum chamber one, 4. Electron beam limiter, 5. Vacuum chamber two, 6. Heterogeneous deflection magnet, 7. Heterogeneous vacuum box, 8. Scintillating fiber optic detector system, 9. Scintillating fiber optic array. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0040] The technical solutions provided by various embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0041] Figure 1 The overall structure diagram of a magnetic spectrometer for measuring the gamma-ray energy-time joint spectrum provided by the present invention is shown in FIG. Figure 1 The above-mentioned magnetic spectrometer for measuring the gamma-ray energy-time joint spectrum specifically includes:

[0042] γ-e conversion target 2, electron beam limiter 4, magnetic analyzer system, scintillation fiber optic detector system 8 and vacuum system.

[0043] The magnetic analyzer system comprises: a heterogeneous deflection magnet 6 and a heterogeneous vacuum box 7 in its magnetic gap.

[0044] The scintillation fiber detector system comprises: a scintillation fiber array 9 for receiving the charged particle beam emitted from the heterogeneous deflection magnet, a photoelectric receiving unit and a data acquisition device.

[0045] The vacuum system includes: a vacuum chamber 1 3 and a vacuum chamber 2 5 .

[0046] Among them, the γ-e conversion target and the electron beam limiter are arranged in the vacuum chamber one, the scintillating fiber array is arranged in the vacuum chamber two, the γ-e conversion target is used to convert the received gamma rays into a charged particle beam, and the special-shaped vacuum box is used to provide a vacuum environment for the charged particle beam in the special-shaped deflection magnet.

[0047] The exit port of the heterogeneous deflection magnet is set to be a quadratic curve, and is provided with an incident edge angle and an exit edge angle;

[0048] The gamma-e conversion target, the electron beam limiter, the heterogeneous deflection magnet and the scintillating optical fiber array are sequentially arranged in the propagation path of the charged particle beam.

[0049] like Figure 1 As shown, the γ-e conversion target, the electron beam limiter, the heterogeneous deflection magnet and the scintillating fiber array are sequentially arranged in the propagation path of the charged particle beam, and the scintillating fiber array is perpendicular to the propagation path of the charged particle beam, that is, the scintillating fiber array is arranged at the bottom of the vacuum chamber 2 along the X direction. The gamma particle beam source 1 is located outside the magnetic spectrometer and is used to generate gamma rays.

[0050] refer to Figure 1 , the physical parameters of the heterogeneous deflection magnet include deflection radius, deflection angle, incident edge angle and exit edge angle.

[0051] Optionally, in this embodiment, the deflection radius is set to 200 mm, the deflection angle is set to 90 degrees, and the incident edge angle and the exit edge angle are set to 61 degrees and 0 degrees respectively.

[0052] The incident edge angle refers to the angle between the incident charged particle beam axis and the part of the incident charged particle beam that is closest to the incident charged particle beam axis.

[0053] The emission edge angle refers to the angle between the part of the emitted charged particles closest to the axis of the emitted charged particle beam and the axis of the emitted charged particle beam. Figure 2 , the deflection radius is Figure 2 As shown in R, the deflection angle is Figure 2 As shown in θ, the angle of the entry edge is Figure 2 As shown in α, the emission edge angle is Figure 2 As shown in β.

[0054] based on Figure 1 A magnetic spectrometer for measuring the gamma-ray energy-time joint spectrum is shown. After the incident gamma particle beam is converted into a charged particle beam by a γ-e conversion target, the charged particles of a special angle are screened by an electronic beam limiter, and then the designed heterogeneous deflection magnet is used to replace the six-pole magnet used in the traditional scheme, and finally the time-intensity waveform of the charged particles is obtained by using a scintillating optical fiber array. Through the above scheme, the charged particle beam can be focused in the Y direction (the direction perpendicular to the plane where the heterogeneous deflection magnet is located) by the edge magnetic field focusing effect of the heterogeneous deflection magnet, and the different exit angles generated by the charged particles after deflection in the deflection magnetic field due to different incident angles are corrected by the curvature of each point of the parabola, so that the exit position of the charged particle beam in the X direction (the direction parallel to the straight line connecting the two end points of the exit port of the heterogeneous deflection magnet) after deflection in the deflection magnetic field is independent of the incident angle, thereby realizing double focusing of the charged particle beam. In addition, the design of the parabolic exit port can increase the path length of particles that deviate from the axis of the charged particle beam in the deflection magnetic field, so that particles on both sides of the axis of the charged particle beam are affected by the focusing effect and the defocusing effect at the same time, thereby being able to replace the traditional six-pole magnet to eliminate the angular dispersion generated by the charged particle beam during the deflection process, thereby realizing the focal plane (the plane formed by connecting the focusing points of the charged particles) perpendicular to the exit direction, and being able to concentrate the dual focusing and angular dispersion elimination capabilities of the charged particles in the deflection magnetic field process on a single magnet, thereby achieving lightweight equipment and high energy resolution conditions while performing time-intensity joint spectrum measurements of gamma rays in a wide energy range (several hundred keV to more than ten MeV).

[0055] Optionally, in one or more embodiments of the present invention, the expression of the parabola is:

[0056] z=-1.38x 2 (1)

[0057] Wherein, z represents the distance between the bottom of the parabola and the straight line connecting the two endpoints of the parabola, and x represents the distance between the two endpoints of the parabola.

[0058] In this embodiment, reference Figure 2 , the vertical direction refers to the Z direction in the direction reference system, and the horizontal direction refers to the X direction in the direction reference system.

[0059] It should be noted that the expression of the above parabola is obtained through multiple simulation experiments after determining the deflection radius, deflection angle, incident edge angle, exit edge angle, distance between the incident port and the γ-e conversion target, and distance between the exit port and the scintillating fiber array of the heterogeneous deflection magnet.

[0060] It should be noted that after the deflection radius, deflection angle, incident edge angle, exit edge angle, distance between the incident port and the γ-e conversion target, and distance between the exit port and the scintillating fiber array are adaptively modified, the quadratic curve expressions obtained are also different. This embodiment is only a quadratic curve expression obtained by multiple simulations after setting a set of parameters, and is not intended to limit the present invention. By modifying any number of the above multiple parameters, different quadratic curve expressions are obtained, which is the same as the principle of this solution and belongs to the protection scope of the present invention.

[0061] This embodiment increases the path length of the charged particles that deviate from the axis of the charged particle beam in the magnetic field by setting the outlet shape of the heterogeneous deflection magnet to a quadratic curve shape. Similarly, the particles on both sides of the axis of the charged particle beam are affected by the focusing effect on one side and the defocusing effect on the other side. It replaces the traditional sextupole magnet and eliminates the role dispersion term in the deflection magnet transmission matrix, thereby improving the overall detection capability of the magnetic spectrometer and greatly reducing the spatial size of the magnetic spectrometer.

[0062] Furthermore, in one or more embodiments of the present invention, the physical parameters of the heterogeneous deflection magnet are obtained based on the horizontal transmission matrix and the vertical transmission matrix of the charged particle beam in the heterogeneous deflection magnet.

[0063] In this embodiment, the principle of obtaining the physical parameters of the heterogeneous deflection magnet according to the horizontal transmission matrix and the vertical transmission matrix of the charged particle beam in the heterogeneous deflection magnet is as follows:

[0064] In a steady magnetic field, charged particles of different energies have different deflection radii, and charged particles with larger energies have larger deflection radii. When the charged particle beam passes through the deflection magnet and reaches the exit, charged particles of different energies are separated, and charged particles of the same energy at different angles converge at different positions horizontally. However, due to the focusing effect of the edge magnetic field, the vertical (perpendicular to the Figure 1 In the X and Z directions, the light will converge into a very small range.

[0065] In the charged particle transmission system, the state of the charged particles is represented by six-dimensional coordinates, and the performance of the system is represented by a six-dimensional transmission matrix. The expression of the six-dimensional coordinates is shown in matrix (2):

[0066]

[0067] Among them, X is a six-dimensional coordinate, x represents the horizontal coordinate of the charged particle, a represents the horizontal angle of the charged particle, y represents the vertical coordinate of the charged particle, b represents the vertical angle of the charged particle, T represents the position coordinate of the charged particle in the transmission direction, and δ represents the deviation of the charged particle energy.

[0068] For the charged particle transmission structure proposed in the present invention, the emission position and emission angle of the charged particles are related to the energy dispersion under the first-order approximation. When the charged particle beam is transmitted in the heterogeneous deflection magnet, not only the lateral motion is coupled with the vertical motion, but also dispersion is generated. The transmission matrix of the charged particle in the magnetic spectrometer that eliminates the angular dispersion is a sixth-order matrix. The transmission matrix of the entire system is shown in matrix (3):

[0069]

[0070] The leading and trailing subscripts of each matrix element represent the row and column of the element. The horizontal position coordinate x and vertical position coordinate y of the charged particle on the image plane can be obtained as shown in Expression (4) and Expression (5) respectively:

[0071] x=M 11 ·x0+M 12 ·a0+M 16 ·δ (4)

[0072] y=M 33 y0+M 34 b0+M 26 ·δ (5)

[0073] Among them, x0 is the horizontal position coordinate of the incident charged particle, y0 is the vertical position coordinate of the incident charged particle. a0 is the horizontal angle of the incident charged particle, b0 is the vertical angle of the incident charged particle, and δ represents the energy deviation of the incident charged particle. In order to achieve double focusing, that is, the position of the charged particle in the focal plane is independent of its initial angle, the angle-related term must be 0 to achieve this, that is, satisfying:

[0074] M 12 =M 34 =0 (6)

[0075] According to the beam transmission theory, the coordinates of the phase space change of charged particles can be expressed as:

[0076] X=M·X0 (7)

[0077] Where X0 is the information of the incident charged particle, and M is the transmission matrix of the charged particle in the heterogeneous deflection magnet.

[0078] Exemplarily, the heterogeneous deflection magnets set according to the above conditions are as follows: Figure 2 As shown; the deflection radius of the magnet is R, the deflection angle is θ, the incident edge angle is α, and the exit edge angle is β.

[0079] For a deflection magnet with a deflection radius of R, a deflection angle of θ, an incident edge angle of α, and an exit edge angle of β, its horizontal transmission matrix M x as follows:

[0080]

[0081] Its vertical transmission matrix is ​​as follows:

[0082]

[0083] It can be obtained that the total transfer matrix from the object point to the image point is:

[0084]

[0085] Where i = 1, 2, 3, j = 1, 2, 3, M 12 The expression is:

[0086]

[0087] Similarly, we can deduce that M 34 The expression is:

[0088]

[0089] Among them, L1 refers to the distance between the incident port of the heterogeneous deflection magnet and the γ-e conversion target, and L2 refers to the distance between the exit port of the heterogeneous deflection magnet and the scintillating fiber array. Since a special second-order curve structure needs to be designed at the exit of the heterogeneous deflection magnet, the exit deflection angle β is 0, and the deflection angle θ is determined to be 90°. The incident deflection angle α and the exit distance L2 can be determined according to the incident distance L1.

[0090] For example, when L1 is determined to be 0.3 meters, α is determined to be 61 degrees and L2 is determined to be 0.58 meters.

[0091] The above is an analysis of the first-order approximation of the impact of charged particles in the transmission process. In the process of charged particle transmission, there are many influencing factors under the second-order approximation, among which the impact of the second-order term of charged particles in the horizontal direction can be expressed as:

[0092]

[0093] The role scatter term M 126 That is, the term (x|aδ) will affect the beam waist plane angle. Under the influence of the angular dispersion term, the point where the charged particle is focused will move along the z-axis in proportion to the energy deviation parameter. Therefore, charged particles with different energy-to-charge ratios are not focused on the Gaussian plane, but along a focal line that is tilted relative to the Gaussian plane (the Gaussian plane is perpendicular to the z-direction). The inclination λ of the focal line (the line connecting the focal points of different charged particles) relative to the Gaussian plane is k It can be expressed as:

[0094]

[0095] Where D k is the linear energy dispersion. In order to make the beam waist plane perpendicular to the emission direction, the character dispersion term must be 0, that is, satisfying:

[0096] M 126 =(x|aδ)=0 (15)

[0097] The characteristic of inclination will affect the system size and resolution of the fiber optic detection system. The traditional method to eliminate the angular dispersion term is to introduce a sextupole magnet. The magnetic field generated by the sextupole magnet will cause the charged particles distributed on both sides of the optical axis to be focused on one side and defocused on the other side, thereby eliminating the angular dispersion term. However, this method takes up a lot of space and is costly.

[0098] This embodiment designs the outlet shape of the deflection magnet to correct the second-order aberration, and uses a second-order curve design instead of a sextupole magnet. The second-order curve at the outlet of the heterogeneous deflection magnet increases the path length of the charged particles that deviate from the optical axis in the deflection magnetic field, and also makes the charged particles on both sides of the optical axis subject to the focusing effect on one side and the defocusing effect on the other side, thereby replacing the sextupole magnet to eliminate the angular dispersion term to improve the overall detection capability, and greatly reduce the space size of the magnetic spectrometer.

[0099] Indicative, Figure 3 A schematic diagram of the motion path of a charged particle beam deflected in a heterogeneous deflection magnet provided by the present invention.

[0100] Depend on Figure 3 It can be seen that the position of the charged particle at the exit of the heterogeneous deflection magnet has nothing to do with the incident angle of the charged particle. The heterogeneous deflection magnet designed in this scheme can achieve double focusing of the charged particle beam and eliminate angular dispersion.

[0101] Furthermore, in one or more embodiments of the present invention, the electron beam limiter includes an inner structure and an outer structure.

[0102] Among them, the materials of the inner layer structure include: graphite and polyethylene; the materials of the outer layer structure include: tungsten, lead, copper, iron and stainless steel.

[0103] In this embodiment, the material of the inner layer structure includes: light materials such as graphite and polyethylene; the material of the outer layer structure includes: tungsten, lead, copper, iron and stainless steel. The inner and outer double-layer structure of the electron beam limiter is used to screen scattered charged particles at special angles. The inner layer of the electron beam limiter is a low-Z material and the outer layer is a high-Z material. Among them, low-Z materials refer to materials with lower atomic numbers, and such materials have higher transparency to X-rays. Generally, low-Z materials include organic materials and polymer materials, etc. Low-Z materials can effectively reduce the bremsstrahlung generated by electrons when shielding electrons. Bremsstrahlung refers to the radiation phenomenon generated by high-speed electrons when they are decelerated. Specifically, when a charged particle (such as an electron) collides with an atom or an atomic nucleus, the velocity of the particle changes due to the electromagnetic field of the atomic nucleus, and part of the kinetic energy is converted into the energy of photons, thereby generating continuous spectrum X-ray radiation. High-Z materials refer to materials with high atomic numbers. High-Z materials have a strong absorption capacity for high-energy radiation such as X-rays. This is because they can interact with radiation particles and convert radiation energy into heat energy or other forms of energy. In addition, high-Z materials have good shielding properties. In applications where radiation shielding is required, such as nuclear facilities and medical radiation therapy rooms, high-Z materials can be used as shielding materials to reduce the impact of radiation on the human body and the environment.

[0104] Through the above scheme, the inner layer structure is designed to be a low-Z material, which can effectively absorb scattered electrons and produce less bremsstrahlung (bremsstrahlung refers to the radiation phenomenon produced by high-speed electrons when they are decelerated). The outer layer structure is designed to be a high-Z material, which can further absorb scattered electrons and shield the X-rays generated when the low-Z material absorbs electrons, thereby achieving a maximized shielding effect.

[0105] In addition, in one or more embodiments of the present invention, the material of the γ-e conversion target is any one of lithium, beryllium, boron, and carbon.

[0106] In this embodiment, the γ-e conversion target is a thin low-Z target. The lower the atomic number, the higher the conversion efficiency. Therefore, lithium is the optimal material for the γ-e conversion target.

[0107] For example, the thickness of the γ-e conversion target can be set to 0.936 mm. When the gamma ray hits the γ-e conversion target, the Compton effect occurs to generate scattered electrons (charged particles).

[0108] This embodiment converts gamma rays into charged particle beams by using a thin low-Z target, which can greatly reduce the absorption of particles in the gamma rays by the γ-e conversion target and improve the conversion efficiency.

[0109] Furthermore, in one or more embodiments of the present invention, the heterogeneous deflection magnet is an electromagnet or a permanent magnet. In the case where the heterogeneous deflection magnet is an electromagnet, the heterogeneous deflection magnet is connected to a power control system.

[0110] The power control system is used to adjust the current in the coil of the heterogeneous deflection magnet to control the magnetic field strength of the heterogeneous deflection magnet.

[0111] This embodiment controls the current in the coil of the heterogeneous deflection magnet through a power supply to control the magnetic field strength of the heterogeneous deflection magnet, which can increase the energy range of the charged particles that are magnetically deflected.

[0112] In addition, in one or more embodiments of the present invention, the relationship between the current in the coil and the central energy of the charged particle beam is expressed as follows:

[0113]

[0114] Where I is the current, w is the central energy of the charged particle beam, in MeV; c represents the speed of light; q is the charge carried by a single charged particle; ε0 is the particle rest energy, L air represents the length of the coil, in meters; μ0 is the magnetic permeability of vacuum, which is 4π×10 -7 ; N represents the total number of turns of the coil; R is the deflection radius.

[0115] Optionally, refer to Figure 1 and Figure 2 In one or more embodiments of the present invention, the gamma ray generated by the gamma particle beam source vertically hits the γ-e conversion target; the distance L1 between the entrance of the heterogeneous deflection magnet and the γ-e conversion target is 0.30 meters; the distance L2 between the exit of the heterogeneous deflection magnet and the scintillating fiber array is 0.58 meters. The charged particle beam generated by the γ-e conversion target passes through the electronic beam limiter and the heterogeneous deflection magnet in sequence, and is absorbed by the scintillating fiber array to obtain the time-intensity waveform and position information, thereby realizing the time-energy joint spectrum detection of the gamma ray.

[0116] The above is a magnetic spectrometer for measuring a gamma-ray energy-time joint spectrum provided by one or more embodiments of the present invention. Based on the same idea, the present invention also provides a method for measuring a gamma-ray energy-time joint spectrum based on the magnetic spectrometer for measuring a gamma-ray energy-time joint spectrum, such as Figure 4 As shown, the method comprises the following steps:

[0117] S10, converting the gamma rays into charged particle beams using a γ-e conversion target.

[0118] S20, using an electronic beam limiter to screen the charged particle beam, and using a heterogeneous deflection magnet to perform double focusing and eliminate angular dispersion on the screened charged particle beam, so that charged particles with different energies in the charged particle beam are separated to different horizontal positions.

[0119] S30, using a scintillating fiber array to receive charged particles separated to different horizontal positions emitted by the heterogeneous deflection magnet, and emitting corresponding numbers of photons based on the energy deposited on the scintillating fiber array by different charged particles.

[0120] S40, using a transmission optical fiber to transmit photons corresponding to different energies to a photoelectric receiving unit, and using a pulse current method for detection, using an oscilloscope and a high-speed data acquisition device to record the output waveform, to obtain horizontal position distribution information about charged particles with different energies, and time and intensity waveform information about the charged particle beam.

[0121] Through the above scheme, incident gamma rays are converted into scattered charged particle rays using scattering targets, scattered electrons at special angles are screened using electronic beam limiters, and double focusing of scattered charged particles is achieved using heterogeneous deflection magnets, and the role dispersion generated by scattered charged particles in the deflection magnetic field transmission process can be eliminated, so that the focal plane is perpendicular to the emission direction, and finally the scattered electron time-intensity waveform is obtained using a scintillating fiber array to obtain high-resolution gamma energy spectrum information and time spectrum information. The measurement requirements of the time-energy joint spectrum of gamma rays are met more efficiently and at a lower cost.

[0122] In addition, in one or more embodiments of the present invention, the type of the heterogeneous deflection magnet is an electromagnet or a permanent magnet. In the case where the type of the heterogeneous deflection magnet is an electromagnet, the method further includes:

[0123] The current value in the coil of the heterogeneous deflection magnet is adjusted to control the heterogeneous deflection magnet to generate magnetic fields of different strengths.

[0124] According to the different strengths of the magnetic field, different ranges of double focusing of the charged particle beam and elimination of angular dispersion are obtained.

[0125] Through the above scheme, the heterogeneous deflection magnets can be controlled to generate magnetic fields of different strengths, obtain different ranges of double focusing and elimination of angular dispersion of charged particle beams, and achieve more accurate measurement of the time-energy joint spectrum of gamma rays of different energies.

[0126] The specific limitations on the implementation method of measuring the gamma-ray energy-time joint spectrum can be found in the above limitations on the magnetic spectrometer for measuring the gamma-ray energy-time joint spectrum, which will not be repeated here.

[0127] When applying the method for measuring the gamma-ray energy-time joint spectrum provided by the present invention, it is not necessary to Figure 4 The steps are executed in the order shown. The specific execution order of the steps can be determined according to needs, and the present invention does not limit this.

[0128] The technical features of the above embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of the present invention.

Claims

1. A magnetic spectrometer for measuring gamma-ray energy-time joint spectrum, characterized in that: It comprises a γ-e conversion target (2) and an electron beam limiter (4) arranged in a first vacuum chamber (3), a magnetic analyzer system arranged in a second vacuum chamber (5), and a scintillation optical fiber detector system (8); The magnetic analyzer system (5) comprises a heterogeneous deflection magnet (6) and a heterogeneous vacuum box (7) arranged in the magnetic gap of the heterogeneous deflection magnet (6); the longitudinal section of the exit port of the heterogeneous deflection magnet (6) is arranged to be parabolic; The γ-e conversion target (2) is used to convert the received gamma rays into a charged particle beam, the electronic beam limiter (4) is used to focus the charged particle beam, and the special-shaped vacuum box (7) is used to provide a vacuum environment for the charged particle beam in the special-shaped deflection magnet (6); The scintillation fiber detector system (8) comprises a scintillation fiber array (9) for receiving a charged particle beam emitted from a heterogeneous deflection magnet (6) and a photoelectric receiving unit for receiving photons emitted by the scintillation fiber array (9); The gamma-e conversion target (2), the electron beam limiter (4), the heterogeneous deflection magnet (6) and the scintillating optical fiber array (9) are sequentially arranged in the propagation path of the charged particle beam.

2. A magnetic spectrometer for measuring gamma-ray energy-time joint spectrum according to claim 1, characterized in that: The expression of the parabola is: z=-1.38x 2 ; Wherein, z represents the distance between the bottom of the parabola and the straight line connecting the two endpoints of the parabola, and x represents the distance between the two endpoints of the parabola.

3. A magnetic spectrometer for measuring gamma-ray energy-time joint spectrum according to claim 1, characterized in that: The deflection radius of the heterogeneous deflection magnet (6) is 200 mm, the deflection angle is 90 degrees, and the incident edge angle and the exit edge angle are 61 degrees and 0 degrees respectively.

4. A magnetic spectrometer for measuring gamma-ray energy-time joint spectrum according to claim 1, characterized in that: The electron beam limiter (4) comprises an inner layer structure and an outer layer structure; Wherein, the materials of the inner layer structure include: graphite and polyethylene; The materials of the outer layer structure include: tungsten, lead, copper, iron and stainless steel.

5. A magnetic spectrometer for measuring gamma-ray energy-time joint spectrum according to claim 1, characterized in that: The material of the γ-e conversion target (2) is any one of lithium, beryllium, boron and carbon.

6. A magnetic spectrometer for measuring gamma-ray energy-time joint spectrum according to claim 1, characterized in that: The type of the heterogeneous deflection magnet (6) is an electromagnet or a permanent magnet. When the type of the heterogeneous deflection magnet (6) is an electromagnet, the heterogeneous deflection magnet (6) is connected to a power supply control system; The power supply control system is used to adjust the current in the coil of the heterogeneous deflection magnet (6) so as to control the magnetic field strength of the heterogeneous deflection magnet (6).

7. A method for measuring a gamma-ray energy-time joint spectrum based on the magnetic spectrometer for measuring a gamma-ray energy-time joint spectrum according to claim 1, characterized in that: include: Converting the gamma rays into charged particle beams using the γ-e conversion target (2); The charged particle beam is screened by the electronic beam limiter (4), and the screened charged particle beam is double-focused and angular dispersion eliminated by the heterogeneous deflection magnet (6), so that charged particles with different energies in the charged particle beam are separated to different horizontal positions; The scintillating optical fiber array (9) receives the charged particles separated to different horizontal positions emitted by the heterogeneous deflection magnet (6), and emits a corresponding number of photons based on the energy deposited by the charged particles at different horizontal positions on the scintillating optical fiber array (9); The photons corresponding to different energies are transmitted to the photoelectric receiving unit by using a transmission optical fiber, and are detected by a pulse current method. An oscilloscope and a high-speed data acquisition device are used to record the output waveform to obtain horizontal position distribution information of the charged particles with different energies and time and intensity waveform information of the charged particle beam. A gamma-ray energy-time joint spectrum is constructed based on the time and intensity waveform information.

8. The method for measuring the gamma-ray energy-time joint spectrum according to claim 7, characterized in that: The type of the heterogeneous deflection magnet (6) is an electromagnet or a permanent magnet. In the case where the type of the heterogeneous deflection magnet (6) is an electromagnet, the method further comprises: Adjusting the current value in the coil of the heterogeneous deflection magnet (6) to control the heterogeneous deflection magnet (6) to generate magnetic fields of different strengths; According to the magnetic fields of different strengths, different energy ranges for performing double focusing on the charged particle beam and eliminating angular dispersion are obtained.

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